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There is ample evidence demonstrating intergroup biases on cognition and emotion. However, it remains unclear how exactly group identification influences these processes, with issues of context sensitivity and goal dependence remaining open to scrutiny. Providing a range of interdisciplinary material, the current review attempts to inform understanding of these issues. Specifically, we provide evidence revealing that individuals show enhanced attention for stimuli associated with an ingroup compared to an outgroup. At the attentional level, such biases can be explained by the assignment of different levels of saliency to ingroup versus outgroup targets. Critically, however, salience assignment is not fixed but varies as a function of context and goal-directed behavior. We suggest that the network in the brain previously associated with social and emotional saliency and attention - notably the anterior insula, posterior superior temporal sulcus, and dorsolateral prefrontal cortex - underpins these effects. Moreover, although attention typically favors ingroup targets, outgroup members can be prioritized on occasion. The implications of this viewpoint and future lines of investigation are considered.

The current research examined the influence of ingroup/outgroup categorization on brain event-related potentials measured during perceptual processing of own- and other-race faces. White participants performed a sequential matching task with upright and inverted faces belonging either to their own race (White) or to another race (Black) and affiliated with either their own university or another university by a preceding visual prime. Results demonstrated that the right-lateralized N170 component evoked by test faces was modulated by race and by social category: the N170 to own-race faces showed a larger inversion effect (i.e., latency delay for inverted faces) when the faces were categorized as other-university rather than own-university members; the N170 to other-race faces showed no modulation of its inversion effect by university affiliation. These results suggest that neural correlates of structural face encoding (as evidenced by the N170 inversion effects) can be modulated by both visual (racial) and nonvisual (social) ingroup/outgroup status.

When people search a display for a target defined by a unique feature, fast saccades are predominantly stimulus-driven whereas slower saccades are primarily goal-driven. Here we use this dissociative pattern to assess whether feature-based selection in patients with lateralized spatial attention deficits is impaired in stimulus-driven processing, goal-driven processing, or both. A group of patients suffering from extinction or neglect after parietal damage, and a group of healthy, age-matched controls, were instructed to make a saccade to a uniquely oriented target line which was presented simultaneously with a differently oriented distractor line. We systematically varied the salience of the target and distractor by changing the orientation of background elements, and used a time-based model to extract stimulus-driven (salience) and goal-driven (target set) components of selection. The results show that the patients exhibited reduced stimulus-driven processing only in the contralesional hemifield, while goal-driven processing was reduced across both hemifields.

We investigated spatial and temporal deficits following brain injury using the temporal order judgement (TOJ) task. Patients judged the order in which two letters appeared to the left and right of fixation. We measured the extent of any spatial bias and the temporal resolution of the decision. Temporal and spatial deficits on the TOJ task were significantly correlated. The spatial bias on the TOJ task was also correlated with the spatial bias on a neglect task and with unilateral deficits on an extinction task, but not with extinction itself. These spatial deficits were all associated with damage to contralateral temporoparietal cortex. In contrast, the temporal resolution of TOJs was linked specifically to deficits in processing multiple stimuli on the neglect and extinction tasks and to damage to the right parietal lobe and the cerebellum. These data suggest that spatial and temporal deficits on the TOJ task reflect different underlying processes.

A single case study of a patient (FK) with utilization disorder following bilateral damage to medial frontal and anterior temporal cortices is reported. FK had to localize a search target following presentation of an earlier verbal or visual cue. Search was strongly affected by semantic/visual associations between the cue and search items. Although FK was unable to name the hue of an incongruent Stroop word, his attention was drawn to a color in the display matching the hue of the cue word. FK's ability to inhibit a response activated by the cueing of attention was impaired. There is dissociation between top-down attention cueing and response inhibition.

We report data examining the relations between endogenous allocation of visual attention and effects of motor-preparation on attention. We tested a patient with a spatial bias in perceptual report following damage to the left inferior parietal lobe and superior temporal gyrus. Previously we have shown that the spatial bias in report can be reduced when a movement is planned to where a target falls in the contralesional field, while the bias is exacerbated when a movement is planned to the ipsilesional side (Kitadono & Humphreys, 2007, Cognitive Neuropsychology, 24). Here we pitted the effects of planning a movement to the contra- or ipsilesional side against the effects of endogenous visual attention, manipulated by varying the probability of where a target would fall. In a no-movement baseline, there was better identification of contralesional targets when there was a good likelihood of targets appearing on the contralesional side (the 20-80 and 50-50 conditions) compared with when targets had a low probability of occurring there (the 80-20 condition). This sensitivity to target probability interacted with the effects of planning a movement to the contra- or ipsilesional side. When the target had a good probability of falling in the contralesional field (the 20-80 and 50-50 conditions), planning a movement to the ipsilesional side disrupted contralesional report. When there was a high probability of an ipsilesional target (the 80-20 condition), planning a movement to a congruent side improved contralesional report. The results indicate that effects of endogenous attention and of motor-based attention influence a common system controlling visual orienting.

The attentional blink, a measure of the temporal dynamics of visual processing, has been documented to be more pronounced following brain lesions that are associated with visual neglect. This suggests that, in addition to their spatial bias in attention, neglect patients may have a prolonged dwell time for attention. Here the attentional dwell time was examined in patients with damage focused on either posterior parietal or frontal cortices. In three experiments, we show that there is an abnormally pronounced attentional dwell time, which does not differ in patients with posterior parietal and with frontal lobe lesions, and this is associated with a measure of selective attention but not with measures of spatial bias in selection. These data occurred both when we attempted to match patients and controls for overall differences in performance and when a single set stimulus exposure was used across participants. In Experiments 1 and 2, requiring report of colour-form conjunctions, there was evidence that the patients were also impaired at temporal binding, showing errors in feature combination across stimuli and in reporting in the correct temporal order. In Experiment 3, requiring only the report of features but introducing task switching led to similar results. The data suggest that damage to a frontoparietal network can compromise temporal selection of visual stimuli; however, this is not necessarily related to a deficit in hemispatial visual attention but it is to impaired target selection. We discuss the implications for understanding visual selection.

Patients with extinction show a characteristic impairment in the identification of objects when two items are presented simultaneously, typically reporting the ipsilesional item only. The effect is thought to be due to a spatial bias advantaging the ipsilesional item under conditions of competing concurrent stimulation. Action relations between objects can result in recovery from extinction as the object pair may be perceived as a single group rather than competing perceptual units. However, objects interacting together can also have implied motion. Here we test whether implied motion is necessary to generate recovery from extinction. We varied orthogonally whether animate and inanimate objects were paired together in positions related or unrelated to action. Implied motion was greater when an animate object was present than when both stimuli were inanimate. Despite this, recovery from extinction was greater when actions were shown between inanimate objects. We suggest that actions between inanimate objects are perceived more easily due to the surfaces of these stimuli being designed for functional goals (e.g., the flat surface of a hammer head is designed to hit the flattened head of a nail). Attention is sensitive to the fit between potential action and the functional properties of objects, and not just to implied motion between stimuli.

Two experiments examined extinction to stimuli presented either with contracting or expanding motion. Experiment 1 used solid shapes which either increased or decreased in size rapidly, consistent with looming motion. Experiment 2 employed random dots so that stimulus size was not confounded with type of motion. In both experiments extinction was modulated by the type of motion presented, with extinction most evident when a contracting object was in the weaker visual field. In addition, in Experiment 2 there was evidence for grouping modulating extinction, when there were looming stimuli in both fields. The results suggest that looming motion is a powerful determinant of stimulus salience in selective attention.

There is a long and ongoing debate about whether subitizing and counting are separable processes. In the present paper we report a single case, MH, who presents with a dissociation in subitizing and counting. MH was spared in his ability to enumerate small numbers accurately along with a marked inability to count larger numbers. We show that non-visual counting was intact and visual counting improved when a motor record of counting could be maintained. Moreover, when larger numbers of items were spatially grouped into 2 subitizable units, performance dramatically improved. However, color grouping did not aid MH's performance, despite his being sensitive to color segmentation. In addition, MH made more re-visits of inspected locations than controls, and he was less aware of a re-visitation being made. The data cannot be explained in terms of general working memory problems (verbal working memory was relatively spared), or general number comprehension problems (e.g., simple sums and counting of auditory items was intact); but they can parsimoniously be accounted for in terms of impaired visuo-spatial memory. The findings support the argument that at least some processes are specific to counting and are not required for subitization - in particular spatial coding and memory for previously inspected locations.

Insights into the functional nature and neuroanatomy of spatial attention have come from research in neglect patients but to date many conflicting results have been reported. The novelty of the current study is that we used voxel-wise analyses based on information from segmented grey and white matter tissue combined with diffusion tensor imaging to decompose neural substrates of different neglect symptoms. Allocentric neglect was associated with damage to posterior cortical regions (posterior superior temporal sulcus, angular, middle temporal and middle occipital gyri). In contrast, egocentric neglect was associated with more anterior cortical damage (middle frontal, postcentral, supramarginal, and superior temporal gyri) and damage within subcortical structures. Damage to intraparietal sulcus (IPS) and the temporo-parietal junction (TPJ) was associated with both forms of neglect. Importantly, we showed that both disorders were associated with white matter lesions suggesting damage within long association and projection pathways such as the superior longitudinal, superior fronto-occipital, inferior longitudinal, and inferior fronto-occipital fascicule, thalamic radiation, and corona radiata. We conclude that distinct cortical regions control attention (a) across space (using an egocentric frame of reference) and (b) within objects (using an allocentric frame of reference), while common cortical regions (TPJ, IPS) and common white matter pathways support interactions across the different cortical regions.

It has been argued that area hMT+/V5 in humans acts as a motion filter, enabling targets defined by a conjunction of motion and form to be efficiently selected. We present data indicating that (a) damage to parietal cortex leads to a selective problem in processing motion-form conjunctions, and (b) that the presence of a structurally and functional intact hMT+/V5 is not sufficient for efficient search for motion-form conjunctions. We suggest that, in addition to motion-processing areas (e.g., hMT+/V5), the posterior parietal cortex is necessary for efficient search with motion-form conjunctions, so that damage to either brain region may bring about deficits in search. We discuss the results in terms of the involvement of the posterior parietal cortex in the top-down guidance of search or in the binding of motion and form information.

What factors determine stimulus-driven responses in patients with utilization behaviour? We examined this question by assessing the influence of an irrelevant cue on visual search in a patient showing evidence of utilization behaviour (F.K.), following bilateral damage to the medial frontal and temporal lobes. Despite being able to repeat the instructions, F.K. often responded to an item in the search display that matched the cue rather than the target. This effect was reduced under certain conditions: (a) when the cue-search interval increased, (b) when F.K. paid less attention to the cue, and (c) when the target discrimination task was made more difficult. On the other hand, the effect arose even when the cue was always invalid. We suggest that information from the cue competed with the top-down set to determine search. F.K.'s lesion makes it difficult for him to impose top-down knowledge rapidly, leading to responses automatically being based on attended, but irrelevant, cues under short cue-display intervals.

The search over time and space (sSoTS) model attempts to simulate both the spatial and the temporal aspects of human visual search using spiking level neurons, which incorporate some biologically plausible aspects of neuronal firing. The model contains pools of units that (a) code basic features of objects, presumed to reside in the ventral visual stream, and (b) respond in a feature-independent way to stimulation at their location, presumed to operate in the posterior parietal cortex. We examined the effects of selective lesioning neurons responding to one side of the location map. Unilateral damage introduced spatial biases into selection that affected conjunction more than single-feature search. In addition, there was an impaired ability to segment stimuli over time as well as space (e.g., in preview search). These results match previously reported data on patients with posterior parietal lesions. In addition we show that spatial biases in selection increase under conditions in which there is decreased activity from excitatory neurotransmitters, mimicking effects of reduced arousal. Further simulations explored the effects of time and of visual grouping on extinction, generating predictions that were then tested empirically. The model provides a framework for linking behavioural data from patients with neural-level determinants of visual attention.

Prader-Willi syndrome (PWS) and Fragile X syndrome (FraX) are associated with distinctive cognitive and behavioural profiles. We examined whether repetitive behaviours in the two syndromes were associated with deficits in specific executive functions. PWS, FraX, and typically developing (TD) children were assessed for executive functioning using the Test of Everyday Attention for Children and an adapted Simon spatial interference task. Relative to the TD children, children with PWS and FraX showed greater costs of attention switching on the Simon task, but after controlling for intellectual ability, these switching deficits were only significant in the PWS group. Children with PWS and FraX also showed significantly increased preference for routine and differing profiles of other specific types of repetitive behaviours. A measure of switch cost from the Simon task was positively correlated to scores on preference for routine questionnaire items and was strongly associated with scores on other items relating to a preference for predictability. It is proposed that a deficit in attention switching is a component of the endophenotypes of both PWS and FraX and is associated with specific behaviours. This proposal is discussed in the context of neurocognitive pathways between genes and behaviour.

In the present paper we show that, in patients with poor semantic representations, the naming of real objects can improve when naming takes place after patients have been asked to use the objects, compared with when they name the objects either from vision or from touch alone, or together. In addition, the patients were strongly affected by action when required to name objects that were used correctly or incorrectly by the examiner. The data suggest that actions can be cued directly from sensory-motor associations, and that patients can then name on the basis of the evoked action.

In order to explore parietal patients' difficulties in the processing of orientation information, we asked parietal patients (N = 8) and healthy and brain-damaged controls to imitate multicomponent actions where object orientation was one component. In Experiment 1 orientation was not the most relevant aspect of the action to be imitated, and the parietal group showed significant difficulties in processing object orientation. However, in Experiment 2, where orientation was placed at the top end of the goal hierarchy, the parietal group were able to process stimulus orientation sufficiently to place it within the goal hierarchy of the action and to reproduce it accurately. We conclude that patients with parietal lesions might be able to include object orientation in a goal hierarchy, but if their processing of orientation information is impaired they might be disproportionately prone to errors when object orientation is lower in the goal hierarchy and so not prioritized for processing resources.

For the first time, we report a spatial bias in visual short-term memory (VSTM) after left medial and inferior occipito-temporal damage. Our patient D.M. showed a spatial bias in report from VSTM, being more accurate at reporting stimuli presented in her left than her right visual field (Experiment 1). This spatial bias could not be attributed to a visual field deficit (Experiment 2) and was based on the relative rather than the absolute locations of the stimuli (Experiment 3). It was reduced when the transfer of items to VSTM was facilitated-for example, by grouping stimuli (Experiment 4) or by reducing the number of items to be remembered (Experiment 5). The spatial bias was attenuated when items moved from right to centre or left to centre, and D.M. was cued to report the item that would have been on the right or left, had the movement continued (Experiment 6). We conclude that posterior ventral damage can impair both the consolidation of new information in VSTM and the explicit report of consolidated information from VSTM.

The ability to recognize individual faces is of crucial social importance for humans and evolutionarily necessary for survival. Consequently, faces may be "special" stimuli, for which we have developed unique modular perceptual and recognition processes. Some of the strongest evidence for face processing being modular comes from cases of prosopagnosia, where patients are unable to recognize faces whilst retaining the ability to recognize other objects. Here we present the case of an acquired prosopagnosic whose poor recognition was linked to a perceptual impairment in face processing. Despite this, she had intact object recognition, even at a subordinate level. She also showed a normal ability to learn and to generalize learning of nonfacial exemplars differing in the nature and arrangement of their parts, along with impaired learning and generalization of facial exemplars. The case provides evidence for modular perceptual processes for faces.

The performance of two patients with visual agnosia was compared across a number of tests examining visual processing. The patients were distinguished by having dorsal and medial ventral extrastriate lesions. While inanimate objects were disadvantaged for the patient with a dorsal extrastriate lesion, animate items are disadvantaged for the patient with the medial ventral extrastriate lesion. The patients also showed contrasting patterns of performance on the Navon Test: The patient with a dorsal extrastriate lesion demonstrated a local bias while the patient with a medial ventral extrastriate lesion had a global bias. We propose that the dorsal and medial ventral visual pathways may be characterized at an extrastriate level by differences in local relative to more global visual processing and that this can link to visually based category-specific deficits in processing.

Spatial information processing with respect to an egocentric reference frame has been shown to recruit a fronto-parietal network along the dorsal stream. The present study investigates how brain lesions in the relevant areas affect the ability to navigate through computer-simulated tunnels shown from a first person perspective. Our results suggest that parietal, but not frontal, patients are impaired in this task. They confused the direction of tunnel turns more frequently and made less accurate judgments about the location of the end position. Errors in map drawing suggest that the impairment may be linked to deficits in updating cognitive heading in the absence of corresponding perceptual information from the virtual environment.

We report a series of 7 experiments examining the interaction between visual perception and action programming, contrasting 2 neuropsychological cases: a case of visual extinction and a case with extinction and optic ataxia. The patients had to make pointing responses to left and right locations, whilst identifying briefly presented shapes. Different patterns of performance emerged with the two cases. The patient with "pure" extinction (i.e., extinction without optic ataxia) showed dramatic effects of action programming on perceptual report. Programming an action to the ipsilesional side increased extinction (on 2-item trials) and tended to induce neglect (on 1-item trials); this was ameliorated when the action was programmed to the contralesional side. Separable effects of using the contralesional hand and pointing to the contralesional side were apparent. In contrast, the optic ataxic patient showed few effects of congruency between the visual stimulus and the action, but extinction when an action was programmed. This effect was particularly marked when actions had to be made to peripheral locations, suggesting that it reflected reduced resources to stimuli. These effects all occurred using stimulus exposures that were completed well before actions were effected. The data demonstrate interactions between action programming and visual perception. Programming an action to the affected side with the contralesional limb reduces "pure" extinction because attention is coupled to the end point of the action. However, in a patient with deficient visuo-motor coupling (optic ataxia), programming an action can increase a spatial deficit by recruiting resources away from perceptual processing. The implications for models of perception and action are discussed.

We provide evidence for long-term priming based on view-specific representations of neglected stimuli. A patient with visual neglect, M.P., was asked to search for a target presented amongst other objects on a table. Subsequently recognition memory was tested for items that were identified and for items missed in search. Items that were missed were rejected more slowly than novel items in the recognition memory task, providing evidence for implicit processing (Experiment 1). Implicit memory for missed items was both item-specific (Experiment 2) and view-specific (Experiment 3), and it was eliminated when there were intervening activities lasting about 1 hour (Experiment 4). There was also an implicit memory for distractors in the search task, which was item- but not view-specific (Experiments 2 and 3) and it lasted for at least an hour, even with other intervening activities (Experiment 4). The data suggest that the representations of neglected stimuli may differ qualitatively from those of nonneglected items, with representations of neglected objects being both view-specific and vulnerable across extended retention intervals. The results support the argument that attention is needed in order to encode object representations that are robust to view transformations and temporal decay or interference.

The 'rubber hand' illusion was induced in a patient showing unilateral visual neglect, with the patient experiencing a shift in the felt position of his right hand towards a contralesional rubber hand. Immediately following the illusion, there were short- lasting reductions in neglect for bisecting about the midline and for cancelling multiple stimuli. No effects were found on the ability to encode briefly presented visual stimuli on the contralesional side. The data demonstrate that the illusion can temporarily alter some aspects of neglect, without altering basic visual encoding. The underlying mechanisms, and the relations to other rehabilitation procedures, are discussed.

We examined the role of the fronto-parietal cortex in top-down modulation of perceptual grouping by proximity, collinearity, and similarity, by recording event related brain potentials from two patients with fronto-parietal lesions and eight controls. We found that grouping by proximity and collinearity in the controls was indexed by short-latency activities over the medial occipital cortex and long-latency activities over the occipito-parietal areas. For the patients, however, both the short- and long-latency activities were eliminated or weakened. The results suggest that the fronto-parietal network is involved in facilitation of both the early and late grouping processes in the human brain.

In neuropsychological research, it is frequently necessary to compare the performance of a single case with that of a control sample. Recently, there has been a discussion about whether existing methods are adequate in preventing Type 1 errors due to increased variability in the single-case data (Crawford, Garthwaite, Howell, & Gray, 2004; Mitchell, Mycroft, & Kay, 2004; Mycroft, Mitchell, & Kay, 2002) and about the power of any comparisons. In this paper, we propose an extension of the modified t test introduced by Crawford and Howell (1998). We provide Monte Carlo simulations that show that it is possible to increase the power of the modified t test by retesting the single case. We also make available a computer program that implements the method introduced in this paper and that can be used by neuropsychologists to test for a difference between a single case and a control group. We apply our procedure to an example of a patient examined on the "Pyramids and Palm Trees" test.

We assessed the factors contributing to local capture in G.K., a patient with Balint's syndrome. G.K. found it difficult to identify the global shape of a compound stimulus, and his poor identification of the global shape was not resolved by introducing familiar local stimuli that were either from the same category as the global target but not tied to a response (Experiment 1) or that belonged to a different category to the target (Experiment 2). Effects of item familiarity were tested by examining local capture from Hebrew letters on compound English letters. Prior to training with the Hebrew letters, G.K. was able to identify the global compounds (Experiment 3a). In contrast, after training with the letters, there was a significant increase in local capture (Experiment 3b). Two additional experiments examined effects of local grouping. Local capture was reduced when the local elements were rectangles or ellipses and grouped by closure of local elements (Experiment 4). Global discrimination also improved when local items were unfamiliar rectangular figure eights (Experiment 5a). However, these grouping effects were counteracted by effects of familiarity when the local elements were changed slightly to become familiar number eights (Experiment 5b). The data suggest that familiar local items are likely to capture spatial attention, whilst grouping by closure between local elements can help global shapes compete for spatial attention with local elements in such patients. The impairment in global perception in Balint's syndrome is not all-or-none but graded according to the factors influencing local capture.

Stankiewicz, Hummel, and Cooper (1998) proposed that detailed coding of part-whole relations for objects is contingent on objects being attended. We report a neuropsychological test of this assertion. We examined the effects of left-right reflection on object matching in a group of patients with parietal damage and impaired attention to the contralesional side of space (Experiment 1). The patients were poor at matching objects subject to left-right reflection, relative to identical stimuli (Experiment 2). This was not due to a lack of sensitivity to information on the contralesional side. In a subsequent study, the patients were better at matching identical whole objects at fixation than when they just received half the object in their ipsilesional field (Experiment 3). However, unlike both nonlesioned controls and control patients with frontal lesions, the parietal patients were unaffected by altering the relative spatial locations of object features in their contralesional field (Experiment 4). The basic result, of poor performance with left-right-reflected items, was also replicated using a priming rather than an explicit matching procedure (Experiment 5). These results provide confirmation that visual attention, mediated by the posterior parietal cortex, is important for generating part-whole codes that facilitate the matching of mirror-reflected objects.

The study of the performance of patients with neurological disorders has been fruitful in revealing the nature and neural basis of inhibition of return (IOR). Thus, in recent years, studies have reported abnormal IOR in patients with Alzheimer's disease, patients diagnosed with schizophrenia, and brain-damaged patients. In the present study, we investigated the hypothesis that a spatial "disengagement deficit" (DD; Posner, Walker, Friedrich, & Rafal, 1984) contributed to the pattern of impaired IOR in the ipsilesional field of parietal patients, found in a previous work (Vivas, Humphreys, & Fuentes, 2003). In a first experiment, we replicated the attenuation of IOR for ipsilesional targets on those trials with a lateralized IOR procedure. With stimuli vertically aligned about fixation, we found intact IOR for both up and down targets. Most important, when we ameliorated the potential impact of a spatial DD by presenting both cues and target in the same hemifield, still we found impaired IOR in the ipsilesional field. We interpret these findings in terms of unilateral parietal damage leading to an imbalance of the relative salience of signals represented in a spatial map for directing attention.

We investigated the effects of long-term training using prism adaptation on a patient with chronic neglect. A positive effect of prism adaptation was apparent on tests of visuo-spatial processing (cancellation, bisection, and grasping), but there was no benefit for neglect on the detection of errors on the contralesional side of words or on the detection the left side of chimeric faces. Across training sessions, the benefit of adaptation on immediate performance decreased, but it increased across sessions and within sessions when performance was tested up to 90 minutes after adaptation. The beneficial effect was maintained up to 1 year posttraining. In later sessions there were also increased negative after-effects following prism adaptation, as training progressed. There was no improvement on tests of mathematical cognition, which comprised an independent deficit in this patient. The data suggest that prolonged prism training can induce long-term adaptive spatial realignment of visuo-motor mappings, ameliorating some aspects of neglect. We discuss the implications for the rehabilitation of neglect and for understanding the neglect syndrome more generally.

Deficits in task switching can be found after frontal lobe damage. Here we demonstrate an impairment in task switching specifically linked to when perceptual weights have to be moved between different dimensions of the same stimulus. A patient (DS) with left frontal lobe damage showed normal performance when he responded to the meaning (a word task) or location (a location task) of a word presented to the left or right of fixation when there was no switching between the tasks. However, when the two tasks were switched every 16 trials in a block, DS showed severe difficulty in performing both tasks (Experiment 1). There were then abnormally large switch costs and effects of stimulus-response congruency. The difficulty was not simply due to switching tasks per se: There were no costs of switching when one of the tasks was modified to have different stimulus displays from the other (Experiment 2). The deficit was also not greater when the switch had to be made from a well-practised task to an unpractised task with more arbitrary stimulus-response mappings, indicating no particular problem in disengaging from a learned task or in configuring new stimulus-response links (Experiment 4). We suggest instead that DS was impaired at shifting attentional weights across different dimensions of the same stimulus, a process required with practised and unpractised tasks alike. The results link this process of shifting attention across stimulus dimensions to the left frontal lobe.

We review evidence on the cognitive neuropsychology of visual object processing, from 1984-2004, dividing the work according to whether it deals with the analysis of visual features, objects, or the relations between object processing and action. Research across this period has led to (1) a more detailed analysis of disorders of feature processing and feature binding, (2) a finer-grained understanding of disorders of object recognition, how these disorders can change over time, and their relations to visual imagery, and (3) new accounts of the relations between vision and action. Cognitive neuropsychological studies have played a key part in furthering our understanding of the functional nature of object processing in the brain.

We report a case-study of YE, a 54-year-old person who suffered multiple shell injuries that caused a right-parietal lesion and left hemianopia, almost 30 years ago. We conducted 4 experiments using a basic extinction paradigm in which YE had to report single stimuli presented on the left or right or two stimuli presented simultaneously in both visual fields. We show that extinction was selectively affected both by increasing the relative perceptual salience of the contralesional stimulus and by cueing attention to the contralesional side. The effects of perceptual salience and attentional cueing interacted, with cueing being more effective when the stimuli had relatively high perceptual salience. The data are consistent with attentional and perceptual factors interacting to determine the competition between left and right side stimuli that underlies extinction.

We contrast naming from pictures, and reading words, for objects and verbs (actions relating to the objects) in a patient with a large, posterior left-hemisphere lesion. We present evidence for spared picture naming for verbs relative to objects, whilst the opposite pattern of sparing occurred in reading. Objects were also spared relative to verbs in tasks requiring that written words be matched to either pictures or auditory words, in the presence of semantically related or unrelated distractors. We conclude that verb semantics were more impaired than semantic knowledge for objects, and that the better semantic knowledge for object names supported word reading. With pictures, however, action verb retrieval was maintained through a nonsemantic route from vision to action, or though preserved right-hemisphere "action semantics."

We report data on patient FK, who presented with a marked deficit in accessing semantic knowledge about objects when tested across a range of input and output modalities. FK also showed a high degree of item-specific consistency in object identification, over and above effects due to object familiarity. We show that, despite being better at naming some objects than others, FK was equally poor at discriminating the superordinate categories of the stimuli. Also, he tended to be better at matching nameable items to a base-level label than to a superordinate-level label. We discuss the implications of the data for models of semantic memory.

Recognition of orally spelt words is an unusual task, not commonly encountered in everyday life, but it can be surprising well preserved in patients with brain damage. There is, however, considerable debate over the cognitive abilities that are required to successfully perform this task. The main controversy has centred on whether oral spelling recognition is parasitic on the processes normally involved in spelling aloud or in reading. We describe a patient (FL) who showed a similar pattern of performance on reading and oral spelling recognition and was better at both tasks relative to spelling. We describe a second patient (FK) who was good at reading and reasonable at spelling but poor at reverse spelling. The patient data are not consistent with either of the following hypotheses: that oral spelling recognition is dependent either on a reading system that is functionally separate from a spelling system, or on a spelling system that is functionally separate from reading. We propose that the findings can, however, be accommodated by a model in which spelling and reading are not functionally independent systems, but share important cognitive components such as a graphemic buffer.

In the present study, the authors examined the effect of tool use in a patient, MP, with neglect of peripersonal space. They found that target detection improved when the patient searched with his arm outstretched, when both visual and motor cues were present. Motor cues (arm outstretched but hidden from view) and visual cues alone (shining a torch on the objects) were less effective. In a final experiment, the authors reported that MP established a better memory for the objects that were searched for when a combined visual and motor cue was present. The authors argue that search was improved by combined visuomotor cuing, which was effective when the action could affect the objects present. Visuomotor cuing also led to stronger memories for searched locations, which reduced any tendency to reexamine positions that had been searched previously. The data are discussed in terms of the interaction between perception and action.

We report the data on effects on visual search of (1) preview displays and (2) singleton targets and distractors in IQ-matched ADHD and control children. All children showed interference from singleton distractors even when targets never carried singleton values. This interference from singleton distractors increased under preview conditions, indicating that the children then had fewer resources available to control attention. There was also one selective deficit for ADHD children; they showed marked problems in responding to singleton targets following preview displays. This suggests that, in ADHD, there is either a selective delay or an impairment in switching attentional sets (from a negative set to the preview to a positive set to a singleton target). We discuss the implications for understanding both ADHD and the development of selective attention.

We report the case of a patient with left parietal damage (MH) who is selectively impaired at both detecting and localising targets defined in terms of their orientation. Performance was relatively good in other tasks where the target was defined either by a single feature (colour) or an orientation conjunction. The results are consistent with the idea that the dorsal stream supports some aspects of basic visual perception (i.e., the discrimination and localisation of orientation-defined targets). The effect of a parietal deficit may be to stress processing via the intact ventral stream, which groups information for object recognition, making differences in orientation less salient. Consistent with this, MH performed better when localising targets at a larger display size, where elements were less likely to group into a familiar shape and where local texture-based processes can come into play. In addition, MH's ability to localise a target was more impaired than his ability to detect a target, supporting the argument that orientation discrimination precedes (or operates independently of) feature localisation.

We report data from a patient, NE, who after surviving encephalitis made misidentification responses to faces known to her premorbidly. NE frequently mistook one famous person for another, one relative for another, and, under some conditions, believed that a picture of a famous person actually depicted one of her relatives. Unlike previously reported patients who have misidentified faces, NE (1) performed reasonably well on tests of facial perception, (2) showed no obvious executive deficits in tests of frontal lobe function, and (3) showed an ability to constrain her misidentification responses in certain situations. A cognitive neuropsychological investigation revealed that NE was able to judge misidentified faces as familiar but failed to access precise semantic information. There were also semantic deficits when knowledge of people was probed through nonvisual modalities-for example, when naming people from definition. We argue that a semantic, as opposed to executive, deficit plays the major (though probably not sole) role in NE's misidentification responses, and we consider how the inter-active activation model of face recognition (Burton, Bruce, & Johnston, 1990) can account for such disorders of person recognition more comprehensively than the Bruce and Young (1986) model.

We examined object identification in two simultanagnosic patients, ES and GK. We show that the patients tended to identify animate objects more accurately than inanimate objects (Experiments 1 and 4). The patients also showed relatively good identification of objects that could be recognised from their global shape, but not objects whose recognition depended on their internal detail (Experiment 2). Indeed, the presence of local segmentation cues disrupted global identification (Experiment 3). Identification was aided, though, by the presence of surface colour and texture (Experiment 4). We suggest that the patients could derive global representations of objects that served to recognise animate items. In contrast, they were impaired at coding parts-based representations for the identification of inanimate objects.

We report data on stored knowledge of everyday tasks in a patient, FK, with 'action disorganisation syndrome'. In section 1, we analysed his explicit knowledge of the component actions, and their temporal order. FK showed generally impaired knowledge of everyday tasks relative to controls, and, when knowledge of the temporal order of the actions was probed, he showed particular impairments for the actions making up the final steps in tasks. In section 2 we assessed FK's implicit knowledge of the tasks, by evaluating how knowledge of the tasks influenced his ability to act out sets of instructions. We demonstrate that FK had some implicit knowledge of the tasks, but also, when actions had to be performed in the order as instructed, there was better knowledge of order for actions performed early rather than late in the task. We suggest that disordered task schema contributed to FK's deficits, with impairments on 'end' actions being vulnerable when task order was important for performance.

We report data on the ability of a patient with Balint's syndrome (GK) to process global information from compound letters. As with other patients with Balint's syndrome, GK was impaired at respond-ing to large, global letters. In Experiment 1 we show that this was due to local capture rather than the absolute size of the stimuli. Also, despite his impairment with global letters, GK showed global inter-ference on local judgements, indicating that some implicit processing took place at the global level. Interestingly, the inability to perceive large global letters was overcome when GK identified a solid, large prime letter prior to the onset of the compound figure (Experiment 2). This priming effect was temporary, and decreased as the interval between the prime and the compound letter increased (Experiment 3). When the prime was an English letter, the effect was maintained even when GK only had to identify the prime's colour, provided a colour-identification block of trials followed rather than preceded a block of trials where prime shapes had to be identified (Experiment 4). In contrast, there was no priming when GK had to identify the colour of English letter primes in a trial block following a block where the task was to identify the colour of Hebrew letter primes (Experiment 5). Overall the data indicate that local capture in Balint's syndrome can be overcome by actively priming a wide attentional window. The results can be interpreted in terms of an interaction between spatial attention and grouping processes that subserves the perception of global compound letters.

The extent to which imagery and perceptual processes overlap in the brain has been the focus of a number of studies using different experimental methodologies (e.g., studies of functional brain activation and studies of patients with selective deficits following brain damage). Here we report the results of a number of different experimental investigations exploring visual memory in a patient with a severe perceptual deficit (HJA). We demonstrate that HJA can perform imagery tasks well that require judgements about a single object or object part; however, he experiences difficulty on tasks where he has to respond to the spatial relations between the local parts of objects. He experiences similar difficulties in perceptual processing. We argue that the bottom-up coding of visual images is influenced by the same intermediate visual processes that serve object recognition.

We examined the relations between selection for perception and selection for action in a patient FK, with bilateral damage to his temporal and medial frontal cortices. The task required a simple grasp response to a common object (a cup) in the presence of a distractor (another cup). The target was cued by colour or location, and FK made manual responses. We examined the effects on performance of cued and uncued dimensions of both the target and the distractor. FK was impaired at perceptually selecting the target when cued by colour, when the target colour but not its location changed on successive trials. The effect was sensitive to the relative orientations of targets and distractors, indicating an effect of action selection on perceptual selection, when perceptual selection was weakly instantiated. The dimension-specific carry-over effect on reaching was enhanced when there was a temporal delay between a cue and the response, and it disappeared when there was a between-trial delay. The results indicate that perceptual and action selection systems interact to determine the efficiency with which actions are selected to particular objects.

We report a case series analysis of a group of seven patients with apparent "category-specific" disorders affecting living things. On standard diagnostic tests, a range of deficits were apparent, with some cases appearing to have impaired visual access to stored knowledge, some with impaired semantic knowledge (across modalities), and some with an impairment primarily at a name retrieval stage. Patients with a semantic deficit were impaired for both visual and associative/functional knowledge about living things, whilst patients with a modality-specific access deficit showed worse performance when stored visual knowledge was probed. In addition, patients with impaired access to visual knowledge were affected when perceptual input was degraded by masking, and all patients showed an interaction between perceptual similarity and category when matching pictures to names or defining statements. We discuss the results in terms of the Hierarchical Interactive Theory (HIT) of object recognition and naming (Humphreys & Forde, 2001). We also discuss evidence on lesion sites in relation to research from functional brain imaging on category differences in object identification in normal observers.

Corticobasal degeneration (CBD) is a progressive disorder that can be characterised by asymmetrical akinetic rigidity, involuntary movements, cortical sensory loss, alien limb syndrome and asymmetrical apraxia (Gibb et al., 1989; Rinnie et al., 1994). Diagnosis of praxic disabilities is thought to be essential for distinguishing CBD, in its early stage, from other akinetic-rigid syndromes. However, the nature of apraxia in CBD, and the relations between ideomotor and ideational apraxia, are not well understood. For example, if there is an ideational deficit in a given patient, does this deficit occur independently of any ideomotor disorder, or are the two impairments linked in some manner? In the present paper we report a case study of a patient with apraxia due to CBD. We examine whether the disorder is confined to production tasks, or whether there is also a related deficit in recognising the correct actions performed with objects (an ideational deficit). We also evaluate whether a disorder found for action with single objects dissociates from the ability to link multiple actions into more complex, everyday tasks. The performance of our patient showed an impairment in both action production and action recognition system, suggesting a component of ideational as well as ideomotor apraxia in CBD.